1. Field of the Invention
The present invention relates to an energy storage device and a method for manufacturing the energy storage device.
Note that the energy storage device refers to all elements and devices which have a function of storing electric power.
2. Description of the Related Art
In recent years, energy storage devices such as lithium ion secondary batteries, lithium ion capacitors, and air cells have been developed.
An electrode for an energy storage device is manufactured by providing an active material over a surface of a current collector. As the active material, a material such as carbon or silicon, which can store and release ions serving as carriers, is used. In particular, silicon or phosphorus-doped silicon has a higher theoretical capacity than carbon, and the use of these materials as the active material is preferable in terms of increasing the capacity of an energy storage device (e.g., Patent Document 1).